It is known that combining a vasoconstrictor with an anesthetic during anesthetic injection reduces the risk of anesthetic toxicity resulting from systemic absorption. In particular, lidocaine may be associated with rare malignant hypothermia and/or cardiovascular collapse and arrest. Use of a vasoconstrictor together with an anesthetic reduces systemic absorption to the anesthetic and increases the anesthetic's local tissue retention time before its eventual dilution via diffusion. It also allows the anesthetic to metabolize more slowly, until local vasoconstriction is reversed.
Currently, epinephrine is most commonly used in combination with lidocaine in concentrations ranging from 0.0000001% to about 0.0001% weight by volume. However, because epinephrine is one of the most powerful alpha 1 agonists, significant cardiovascular side effects may occur, with an increased risk of hypertension, stroke, arrhythmia or infarction, particularly, in individuals with a history of cardiovascular disease. This risk increases exponentially in cases where an inadvertent intraarteriolar injection may occur, which may happen especially when the anesthetic injection is used for regional nerve block.
Accordingly, there is a need to optimize vasoconstriction during anesthesia without systemic negative side effects caused by epinephrine.